In recent years the use of fiber reinforced resin composites in the aerospace field has become more and more widespread. Such composites are usually formed by laying down fiber rovings (e.g., fiber yarn) preimpregnated with epoxy resin. At present, the preferred fiber used to form the rovings is graphite filament fiber. The rovings are laid downside by side, i.e., in parallel to create layers. The layers are oriented at different angles with respect to one another, the angles and number of layers running in each direction depending upon the directional strength requirements of the resultant structure. After a structure is laid up, it is placed in an autoclave and the resin cured.
Fiber reinforced resin composite technology has been used to create a wide variety of airframe structural elements, many of which have airfoil shapes -- flaps, ailerons, elevators and rudders, for examples. The entire airframe of some aircraft, including the fuselage, wings and horizontal and vertical stabilizers, have been formed entirely of fiber reinforced resin composites.
While fiber reinforced resin composites have strength and weight advantages over more traditional airframe materials, such as aluminum, they have certain manufacturing disadvantages. Specifically, because aluminum is malleable, it can be easily bent into various airfoil shapes and configurations. Contrariwise, after being cured, fiber reinforced resin composites are not malleable. As a result, fiber reinforced resin composites must be configured prior to curing. The configuring of fiber reinforced resin composites is normally accomplished by laying the fiber rovings atop a form, commonly referred to as a tool. After a suitable number of fiber roving layers have been "laid up," the tool is placed in the autoclave with the layup while the layup resin is cured.
Prior to the present invention, fiber reinforced resin composite layups have been formed by laying down strips of fiber roving tape by hand or using a machine designed for such a purpose. U.S. Pat. No. 4,461,669 discloses a machine for laying down strips of fiber roving tape. Fiber roving tape is formed of a plurality of parallel oriented rovings impregnated with resin mounted on a backing material or in some other manner held together.
The major disadvantage of the use of tapes to create fiber reinforced resin composites relates to the lack of flexibility inherent in tapes. Because tapes are formed of rovings of equal length held together by a backing paper, it is extremely difficult if not impossible to steer the tape in the plane of the tape. That is, it is most difficult to create a smooth curve in the plane of the tape except at extremely hard large radiuses of curvature. Further, because the rovings that form the tape are held together, it is difficult if not impossible to decrease the width of a section of tape as it is being dispensed. As a result, it is difficult to change width and/or thickness of the resultant composite in a smooth manner. The invention is directed to overcoming these and other disadvantages associated with the laying up of fiber reinforced resin composites.